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Applied and Environmental Microbiology, August 2009, p. 5273-5283, Vol. 75, No. 16
0099-2240/09/$08.00+0     doi:10.1128/AEM.00774-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Inactivation of PadR, the Repressor of the Phenolic Acid Stress Response, by Molecular Interaction with Usp1, a Universal Stress Protein from Lactobacillus plantarum, in Escherichia coli

Jérôme Gury ,^, Hélène Seraut, Ngoc Phuong Tran, Lise Barthelmebs,^¶ Stéphanie Weidmann,^|| Patrick Gervais, and Jean-François Cavin^*

Laboratoire GPMA EA4181 IFR92, AgroSup Dijon ENSBANA, 1 Esplanade Erasme, Université de Bourgogne, F-21000 Dijon, France

Received 6 April 2009/ Accepted 12 June 2009

The phenolic acid decarboxylase gene padA is involved in the phenolic acid stress response (PASR) in gram-positive bacteria. In Lactobacillus plantarum, the padR gene encodes the negative transcriptional regulator of padA and is cotranscribed with a downstream gene, usp1, which encodes a putative universal stress protein (USP), Usp1, of unknown function. The usp1 gene is overexpressed during the PASR. However, the role and the mechanism of action of the USPs are unknown in gram-positive bacteria. Therefore, to gain insights into the role of USPs in the PASR; (i) a usp1 deletion mutant was constructed; (ii) the two genes padR and usp1 were coexpressed with padA under its own promoter as a reporter gene in Escherichia coli; and (iii) molecular in vitro interactions between the PadR, Usp1, and the padA promoter were studied. Although the usp1 mutant strain retained phenolic acid-dependent PAD activity, it displayed a greater sensitivity to strong acidic conditions compared to that of the wild-type strain. PadR cannot be inactivated directly by phenolic acid in E. coli recombinant cultures but is inactivated by Usp1 when the two proteins are coexpressed in E. coli. The PadR inactivation observed in recombinant E. coli cells was supported by electrophoretic mobility shift assays. Although Usp1 seems not to be absolutely required for the PASR, its capacity to inactivate PadR indicates that it could serve as an important mediator in acid stress response mechanisms through its capacity to interact with transcriptional regulators.

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* Corresponding author. Mailing address: Laboratoire GPMA EA4181 IFR92, AgroSup Dijon ENSBANA, 1 Esplanade Erasme, Université de Bourgogne, F-21000 Dijon, France. Phone: (33) 3 80 39 66 72. Fax: (33) 3 80 39 66 40. E-mail: cavinjf{at}u-bourgogne.fr

Published ahead of print on 19 June 2009.

J.G. and H.S. contributed equally to this study.

Present address: UMR CNRS 5557, Université Lyon I, 69622 Villeurbanne, France.

Present address: IGM Bât. 409 Université Paris-Sud 11, F-91405 Orsay Cedex, France.

^¶ Present address: IMAGES EA 4218, Centre de Phytopharmacie, Université de Perpignan Via Domitia, 52 Ave. Paul Alduy, 66860 Perpignan Cedex, France.

^|| Present address: Laboratoire REVV, IFR92, Institut Jules Guyot, Université de Bourgogne, 21000 Dijon, France.

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Applied and Environmental Microbiology, August 2009, p. 5273-5283, Vol. 75, No. 16
0099-2240/09/$08.00+0     doi:10.1128/AEM.00774-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.